You probably already know this, but it came as a pleasant surprise to me: the very detailed topo maps on Natural Resources Canada can easily be saved as PDFs for offline use. Here is the link that will get you started:
The interface is pretty intuitive -- the only trick is that when you have drilled down to the area you want, it is easier to click "print" than to click "save." The print dialogue box gave me an option to save as pdf -- not sure if this is a function of the website or of my own computer. (I am not much of a tech wizard, obviously.)
The pdf gives me the ability to look at the map, even when I don't have wifi. The downside, of course, is that I would have to know where I am headed while I am in town with a wifi connection; often, our hiking plans change at the last minute, so that may be a bit of a problem.
The other hitch is that the NRC website is very slow, and the files are fairly large -- I have an urban fiber optic connection, and each map took ten or 15 seconds to load. Not sure how this will play out when we are in some coffee shop in a small town in the Rockies!
They are nice maps though it takes about 20 to 25 seconds to load on my slow DSL (1.5 M) line.
unfortently I haven't yet figured out a way to seam multiple maps together. So when I download a map that has sufficient resolution to see the detail I need, I can't see (or save) a big enough area to be of use to me. Please let me know if you have this problem licked.
Answering Steve's question, I do not know how to seam the PDFs. I just figured I would toggle from one map to the next. Not ideal, but better than nothing. This afternoon my tech wizard son is going to teach me how to install PDFs onto an iPhone, so that it works even if we are not in cell range. Sounds like magic, but I await enlightenment.
My son created a Dropbox account for me -- my pdfs on the computer go into the dropbox, and it synchs up with the iphone via wifi. I then turn off the wifi when we are in the boonies to save the battery on the iphone, but the pdfs are still usable.